1. Field of the Invention
The present invention relates to a completely novel ion generator and image forming apparatus which are used for a rewritable paper and a writing device such as an electrostatic recording device, etc.
2. Prior Art
Among various recording devices, electrophotographic recording devices employ a non-impact recording method and have features in that the noise level is low, characters can be recorded clearly, the recording rate is high, and the running cost is comparatively low. Therefore, recently, they have been used as output terminal devices of OA equipment, and their market also has been rapidly expanding.
An outline of the electrophotographic recording devices is described by showing the construction of the recording part of a laser beam printer as one of the electrophotographic recoding devices in FIG. 6. In an electrophotographic recording device, first, as shown in FIG. 6, in normal cases, a photoconductor drum 100 is used. The entire surface of the photoconductor drum 100 is uniformly charged to, for example, approx. −800 V by negative charge by a charging device 101 consisting of a corona charger. Then, the photoconductor drum 100 is irradiated with a laser beam 102 in response to an image signal. The photoconductor drum 100 lowers in resistance only at a portion irradiated with a beam, so that the negative charge on the portion irradiated with the laser beam 102 is erased to form an electrostatic latent image. Normally, as the laser, one semiconductor laser is used, and a beam modulated according to the image is scanned by a rotating polygon mirror (not shown). The electrostatic latent image thus formed is developed by a developing device 103. Namely, to the portion of the electrostatic latent image on the photoconductor drum 100 where the negative charge has been erased, toner of coloring fine particles negatively charged by reversal development adheres by being applied with a bias of approximately −300 V, whereby the electrostatic latent image is visualized.
A recording sheet 105 taken out of a paper cassette that is not shown by paper feed rollers 104 is conveyed in timing with the image signal and comes into contact with the photoconductor drum 100. At this point, the visualized toner image is transferred onto the recording sheet 105. On a transfer charger 106, a positive charge is supplied from, for example, the back side of the recording sheet 105, whereby the image developed by the negatively charged toner on the photoconductor drum 100 is attracted onto the recording sheet 105 and transferred thereon. The recording sheet 105 on which the image has been transferred is separated from the photoconductor drum 100 by a separating charger 107. Last, the toner is fixed onto the recording sheet 105 by being heated and pressurized by a fixing device 111 consisting of heat rollers 110, etc., and then recording is ended.
On the photoconductor drum 100, remaining toner that has not been transferred onto the recording sheet 105 still remains. After the photoconductor drum 100 is cleaned by scraping-off such remaining toner by a cleaner 108, the surface of the photoconductor drum 100 is entirely exposed by an erasing lamp 109 consisting of an LED, etc., to erase the charge.
Thus, the electrophotographic recording device forms an image through the steps of charging, latent image forming, developing, transferring, and fixing. Last, the photoconductor drum 100 is completely cleaned through the cleaning step and becomes reusable. Each step may slightly differ depending on the device type, however, the steps as described above are basically employed.
In these electrophotographic recording devices, as described above, in order to form an electrostatic latent image, a photoconductor drum 100 made of an organic material or an inorganic material as an optical semiconductor is necessary. Such a photoconductor drum 100 is an optical semiconductor, and is formed from a functional material having a resistance that changes when irradiated with a beam, weakness against heat, and easily lowers in sensitivity due to a long period of irradiation of a beam, and has a short life, and is high in cost due to its complicated construction. Furthermore, in order to form an electrostatic latent image by irradiating the photoconductor drum 100 with a laser beam 102, a laser unit having a rotating polygon mirror (not shown) is necessary. This laser unit requires rotation of a rotating polygon mirror with accuracy at a constant high speed, and is very expensive and large in size.
The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a method for controlling ion generation, which is controllable by a low voltage, an ion generator and an image forming apparatus equipped therewith, which are sized as small as possible and can form an electrostatic latent image at low cost.